The fabrication of light-emitting diodes (LEDs) and other high-performance devices, such as laser diodes, optical detectors, and field effect transistors, typically utilizes a vacuum deposition process (e.g., physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), etc.), to grow a thin film stack structure of group-III nitride (or other materials) over a sapphire, silicon carbide, or silicon substrate. A thin-film vacuum deposition tool includes a process chamber, which is a sealed environment that allows infused gases to be deposited upon the substrate (typically in the form of wafers) to grow the thin film layers. An example of a current product line of such manufacturing equipment is the Impulse™ PVD AlN Chamber for deposition of a high quality aluminum nitride (AlN) buffer for gallium nitride LED, manufactured by Applied Materials Inc.
Substrate carriers support one or more substrates (such as wafers) and are used to transport and hold the one or more wafers inside furnaces, CVD and PVD process chambers, and/or other equipment. The carriers are frequently made of materials such as silicon carbide, silicon, or silicon carbide coated graphite, which allow them to be used at the elevated temperatures inside furnaces while the wafers are being processed. Depending on the materials that carriers are made of, the carriers can change size and/or deform (e.g., by “bowing”) over time while exposed to elevated temperatures. This can pose a problem to substrate handling automation. Additionally, these carriers are also limited in their useful temperature range. In certain processes, some commonly used materials cannot be used because the carrier would deform to an unusable state rather quickly. If the carriers change dimensionally after a period of time due to the stresses of the fabrication processes, they could prove to be unusable in the substrate loading equipment.
Wafers having a diameter of 8 inches or more are commonly used in the semiconductor industry for the manufacture of integrated circuits. However, for such specialized devices as LEDs, sapphire wafers having a diameter smaller than 8 inches are often specified. Substrate carriers are typically configured to support a wafer or substrate of a given size, e.g., a given diameter. Thus, different substrate carriers are typically provided to support substrates of differing dimensions, which leads to increase in cost and complexity of substrate processing equipment.
Thus, the inventors have provided embodiments of improved substrate carriers that address one or more of the above disadvantages.